Impact of Contamination from Scattered Photons in Singles-Mode Transmission Data on Quantitative Small-Animal PET Imaging

In previouswork,wedescribed and validated amethod of scatter correction for singles-mode transmission data using experimen-tal preinjection data acquired with a dedicated rodent PET scan-ner. In thecurrentwork,we investigated the impact that ourmethod has on the quantitative accuracy of small-animal PET.Methods: This investigation had 3 stages. We first confirmed the general validity of our method by applying it to preinjection transmission data from a different imaging system (a larger dedicated primate scanner). For these data, we evaluated the accuracy of the reconstructed distributions of linear attenuation coefficients (m-values). In the second stage, we applied our attenuation-map reconstruction and scatter correction procedure for postin-jection transmission data acquired with the dedicated rodent scanner. For these studies, we investigated the quantitative ac-curacy of reconstructed emission images that use attenuation correction derived from postinjection transmission data. In the third stage, we compared our scatter correction method with 2 more commonly used alternatives (automated rescaling and segmentation of the attenuation-map images). Results: For the primate scanner data, the average reconstructed m-values with scatter correction were within 3 % of the expected values for wa-ter and soft tissue, whereas uncorrected values were 19%–26% lower than their expected values. For the postinjection transmis-sion studies, we found that the correct average m-values and reconstructed activity concentrations consistent with well-counter measurements were obtained only when scatter correc-tion and emission contamination correction were applied to the transmission data. We also found that our transmission scatter correction provides more accurate m-values and better image quantification than either rescaling or segmentation. Conclu-sion: Using different imaging systems (primate and rodent) and different scanning protocols (before and after injection), we found that our transmission scatter correction is more accurate (for both reconstructed m-values and activity concentrations) than the existing alternatives